An intrusion detection device has been developed which detects a motion of a person in a specific area such as indoors. As an example of an intrusion detection method, a method using a propagation delay profile, i.e., a power delay profile, of UWB-IR (Ultra WideBand-Impulse Radio) is disclosed in “Study on Indoor Human Body Detection Using UWB-IR”, Keiji Terasaka et al., The Transactions of the Institute of Electronics, Information and Communication Engineers B, Vol. J90-B, No. 1, pp. 97 to 100, Jan. 1, 2007 (Non-Patent Literature 1), for example.
In the method disclosed in Non-Patent Literature 1, however, since a broadband signal is used, interference with other radio services becomes a problem. Further, since a power of a received signal is used, indoor multipath fading may occur, which may cause degradation of detection accuracy.
As a technique for resolving the above problems, Japanese Laid-Open Patent Publication No. 2008-216152 (Patent Literature 1) discloses a configuration as follows. That is, an event detection apparatus calculates an eigenvector, i.e., an arrival angle distribution, based on a signal received by an array antenna, and calculates an inner product of the calculated eigenvector and an eigenvector during normal time which is a comparison reference. Then, based on a result of comparison of the inner product with a predetermined threshold, the event detection apparatus detects occurrence of an event, i.e., an intruder:
Meanwhile, as an example of a detection device for a vehicle which detects a motion of a person and warns that abnormality occurs in the vehicle, there is disclosed a technique in which an ultrasonic sensor installed in a vehicle detects occurrence of abnormality in the vehicle such as a criminal's breaking glass and entering the vehicle and sounds a siren (Non-Patent Literature 2).